LIGHT EMITTING DEVICE

Abstract

A light emitting device includes a substrate and a light emitting unit. The light emitting unit is over the substrate. The light emitting unit includes a light emitting subpixel and an electrode. The electrode is stacked on the light emitting subpixel along a direction. Moreover, the electrode includes a dimension measured perpendicular to the direction and the dimension is not greater than about 8 um.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority of U.S. Provisional Patent Application Ser. No. 62/487,097, filed on Apr. 19, 2017, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to light emitting device, especially to an organic light emitting device and manufacturing method thereof.

BACKGROUND

Flat panel display becomes more popular in recent years and is widely adopted from pocket sized electronic devices, such as cell phone, to a wall mount big screen television. Similar to the increasing demanding on the transistor density for IC (Integrated Circuit), the resolution requirement for a display has also been elevated. In recent trend, organic light emitting material is introduced as a light source in flat panel to enhance the possibility of foldability. To select the electrode for the organic light emitting material is challenge to a flexible panel designer. For most flat panels, ITO or IZO are commonly used as a top electrode for the lighting source when considering transparency and resistivity. However, the poor performance on flexibility is a concern when the panel is deformed.

SUMMARY

A light emitting device includes a substrate and a light emitting unit. The light emitting unit is over the substrate. The light emitting unit includes a light emitting subpixel and an electrode. The electrode is stacked on the light emitting subpixel along a direction. Moreover, the electrode includes a dimension measured perpendicular to the direction and the dimension is not greater than about 8 um.

In some embodiments, the electrode is a cathode of the light emitting unit. The light emitting device further includes an optical sensor adjacent to the light emitting unit and configured to detect emission intensity of the light emitting unit.

In some embodiments, the light emitting device further includes an array of thin film transistors (TFT) under the light emitting unit and the optical sensor is electrically connected to the TFT. The light emitting device further includes a stopper adjacent to the light emitting unit, wherein, along the direction, the stopper has a thickness being greater than a thickness of the light emitting unit. In some embodiments, the light emitting device further includes a through via in the stopper.

In some embodiments, a light emitting device includes a substrate and an array of light emitting units over the substrate. Each light emitting unit of the array includes an electrode and a light emitting layer between the electrode and the substrate, wherein a top view area of the electrode is substantially equal to a top view area of the light emitting layer.

In some embodiments, the light emitting device further includes an insulation material filling a space between adjacent light emitting units. The light emitting device further includes a conductive trace to connect electrodes in a string. The light emitting device further includes an array of optical sensors, wherein each of the optical sensors is assigned to a corresponding light emitting unit. In some embodiments, the light emitting device further includes an array of stoppers, wherein each stopper is between two adjacent light emitting units. In some embodiments, the light emitting device further includes a conductive trace electrically connecting each optical sensor to a circuit in the substrate. In some embodiments, the light emitting device further includes a touch sensor over the array of light emitting units, and an insulation layer between the touch sensor and the array of light emitting units.

In some embodiments, the light emitting device further wherein the touch sensor is surrounded by a plurality of light emitting units from a top view perspective. In some embodiments, the light emitting device wherein the touch sensor is laterally offset from the plurality of light emitting units from a top view perspective. In some embodiments, the light emitting device further includes an array of optical sensors over the array of light emitting units, wherein the array of optical sensors are configured to detect ambient light emitted into the light emitting device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flexible light emitting device.

FIG. 2 is top view of a portion of a flexible light emitting device according to an embodiment.

FIG. 3 is top view of a portion of a flexible light emitting device according to an embodiment.

FIG. 4 is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 5 is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 6 is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 6A is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 7 is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 8A is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 8B is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 9 is cross sectional view of a portion of a flexible light emitting device according to an embodiment.

FIG. 10 is top view of a portion of a flexible light emitting device according to an embodiment.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure is to introduce a method being capable of manufacturing a high density light emitting display. In the disclosure, the term “high density” is defined as the lighting pixel density is at least equal or greater than 800 ppi. However, the method is also applied for light emitting display with pixel density lower than 800 ppi.

The present disclosure is to provide a new design of an electrode for an organic light emitting material used in a flexible panel. The electrode has a suitable dimension is order to minimize the reflection of the ambient light. Material of the electrode also has a high flexibility and low resistivity so as to make the flexible panel foldable and low power consumption. Through the present disclosure, a flat panel designer can have a much greater window to allocate the driving circuit, touch panel wires within the light emitting pixel array.

FIG. 1 illustrates an embodiment of an electronic device 10. The electronic device 10 can be a rigid or a flexible display. Display 10 can have at least four different layers substantially stacked along a thickness direction X. Layer 12 is a substrate configured as a platform to have a display layer 14 disposed thereon. Layer 16 is a cap layer to be disposed on the light emitting layer 14 and layer 18 is configured as a window for light emitting in/out the electronic device 10. In some embodiments, layer 16 is an encapsulation layer. Layer 18 can also be configured as a touch interface for the user, therefore the surface hardness of the might be high enough to meet the design requirement. In some embodiments, layer 16 and layer 18 are integrated into one layer.

Layer 12 might be formed with a polymer matrix material. Layer 12 has a minimum bend radius around about 3 mm. The minimum bend radius is measured to the inside curvature, is the minimum radius one can bend layer 12 without kinking it, damaging it, or shortening its life. In some embodiments, several conductive traces may be disposed in layer 12 and form circuitry to provide current to the light emitting layer 14. In some embodiments, a thin film transistor (TFT) is disposed on layer 12 and located between layer 12 and light emitting layer 14. In some embodiments, the TFT can be embedded into layer 12 and integrated as a whole.

FIG. 2 is a top view of the light emitting layer 14 in one embodiment. The light emitting layer has a surface 140. An array of light emitting units including light emitting unit 145a, 145b, and 145c disposed on the surface 140. Each light emitting unit is supplied with current through conductive trace 142. In one embodiments, some light emitting units such as 145a, 145b, and 145c are arranged in a column and connected in series by the conductive trace 142. The serial connected light emitting units can be further electrically connected with an electrode 146. The electrode 146 may be disposed at a peripheral region of the surface 140. The substrate layer 12 may be disposed under the light emitting layer 14.

FIG. 3 is a top view of the light emitting layer 14 in another embodiment. In addition to the light emitting units, a stopper 147 is disposed between two adjacent light emitting units. In another embodiment, an optical sensor 150 is also disposed adjacent to a light emitting unit. In some embodiments, the optical sensor 150 is disposed on al stopper 147 (as shown in the lower left corner). In some embodiments, a circuitry 156 configured to drive the array of light emitting units is on the surface 140 and inserted between the light emitting units.

FIG. 4 is a cross sectional view along line AA in FIG. 2. A layer 12a having TFT or other circuitries can be disposed on the substrate 12. A top surface of the layer 12a is configured as a surface 140 for the light emitting layer. There are two light emitting units 145 disposed on the surface 140. Each light emitting unit has a light emitting subpixel 145-2 and an electrode 145-1 disposed over the light emitting subpixel 145-2.

Electrode 145-1 provides electric current to the light emitting subpixel 145-2. The light emitting subpixel 145-2 can emit light through the electrode 145-1 and also emit through layer 16 and layer 18, then reached user's eyes. In some embodiments, the electrode 145-1 is a cathode connected to the light emitting subpixel 145-2. As shown in FIG. 2, in some embodiments, each electrode 145-1 is connected to a conductive trace 142 in order to provide electric current to a corresponding light emitting subpixel 145-2.

Electrode 145-1 includes conductive material and in some embodiments electrode 145-1 includes metallic elements such as Mg, Al, Ag, Au, Cu, W, etc. In some embodiments, electrode 145-1 substantially includes Ag and Mg.

Electrode 145-1 has a thickness d vertical to the surface 140. The thickness d is designed to have a transmittance around 80% for the light emitting from the light emitting subpixel 145-2. Moreover, the thickness d might be adjusted according to the wavelength of the light emitting from a corresponding light emitting subpixel, which is located right between the electrode 145-1 and the substrate 12. In some embodiments, a thickness of electrode 145-1 is between about 200 Å and about 400 Å. In some embodiments, a thickness of electrode 145-1 is between about 250 Å and about 350 Å. In some embodiments, a thickness of electrode 145-1 is between about 275 Å and about 325 Å.

Electrode 145-1 can be designed to cover the whole lateral surface (surface interfacing electrode 145-1) of the light emitting subpixel 145-2 in order to provide a uniform current density to the light emitting subpixel 145-2. However, in some embodiments, area of a lateral surface of the electrode 145-1 can be different from the lateral surface of the light emitting subpixel 145-2. Electrode 145-1 has a width w, which is measured in a direction substantially vertical to the stacking direction of layer 12 and layer 14 in FIG. 1. In some embodiments, the width w is not greater than 8 um. In some embodiments, the width w is not greater than 5 um.

In some embodiments, the light emitting subpixels can emit at least three different colors, red, green, and blue. In some embodiments, each light emitting subpixel has a lateral width substantially equal to the width, w, of the electrode 145-1.

Adjacent light emitting units 145 are separated with a space s. The space s can be measured from adjacent electrodes 145-1 or adjacent light emitting subpixels 145-2 depending on the design. In some embodiments, space s is between about 2 nm and about 100 um. In some embodiments, space s is not greater than about 50 um.

From FIG. 2, person with skill in the art should appreciate that the electrode is only disposed on a limited area, which may be substantially to the area of the corresponding light emitting subpixel. The corresponding light emitting subpixel is defined as the light emitting subpixel disposed right under the electrode. In other words, as long as the electrode can supply uniform electric current to the light emitting subpixel, the area or width of the electrode is preferred to be less. For some embodiments, the area of the electrode is designed to be just great enough to cover the lateral surface of the corresponding light emitting subpixel.

The electrode design mentioned above is called a patterned electrode design. Instead of a blanket electrode to substantially cover the surface 140, the present disclosure use patterned electrode to minimize reflection of lights from the ambient, which usually enter into the device 10 through the window layer 18 in FIG. 1. Entered ambient light might be reflected by the patterned electrodes but the reflection can be neglected from a human's eye since the width of the each electrode is small, not greater than 8 um.

FIG. 5 is a cross sectional view along line BB in FIG. 3. Numeral labels used in FIG. 4 represent same elements and are not repeatedly introduced herein. In some embodiments, the stopper 147 has a thickness t, which may be greater than the total thickness of an adjacent electrode 145-1 and light emitting subpixel 145-2. While stacking layer 16 or layer 18 over the light emitting layer 14 as in FIG. 1, layer 16 or layer 18 may contact the stopper 147 to prevent the layer 16 or layer 18 from touching the electrode 145-1. Therefore, damage is avoided when a user is pressing the layer 18 or layer 16. Insulation material can be filled into the space between the stopper 147 and the electrode 145-1.

FIG. 6 is a cross sectional view along line CC in FIG. 3. The optical sensor 150 is disposed adjacent to the light emitting subpixel 145-2. In the present embodiment, the optical sensor 150 is disposed on the stopper 147. The optical sensor 150 is configured to detect the intensity of light emitted from the light emitting subpixel 145-2. As in FIG. 3, each optical sensor 150 is configured to detect the intensity of one light emitting subpixel 145-2, which may be most adjacent to that optical sensor 150. As in FIG. 6, the light emitting subpixel 145-2 right to the optical sensor 150 is designated.

In some embodiments, for an array of light emitting subpixels, each light emitting subpixel in the array is assigned with an optical sensor. Each optical sensor can monitor the performance of a corresponding light emitting subpixel in a real time mode. Therefore, if a light emitting subpixel is found to be under-performed, for example, lower intensity, by the corresponding optical sensor, compensation current can be added to the light emitting subpixel in order to bring the performance back to desired value. The optical sensor can be further electrically connected to a driver, which can decide when and how to supply a compensation current to the light emitting subpixel. In some embodiments, the compensation is performed either in active or offline mode.

The optical sensor 150 can be electrically connected to the substrate 12 or the TFT layer 12a. Performance of light emitting subpixel detected by the optical sensor 150 can be converted into electrical signal, which is delivered to the substrate 12 or the TFT layer 12a. As in FIG. 6A, the electrical signal from the optical sensor 150 can be conducted to the TFT layer 12a either through a via 160 or a conductive trace 162. Via 160 can be formed in the stopper 147 as shown in the drawing. The electrical signal from the optical sensor 150 can be conducted to the TFT layer 12a or other location through a conductive trace 164. In some embodiments, the TFT layer also includes a circuitry to measure the performance of the light emitting subpixel.

FIG. 7 shows another embodiment having a second optical sensor 152. The second optical sensor 152 is disposed on an insulation layer 148, which is disposed to surround the electrode 145-1 and light emitting subpixel 145-2. The insulation layer 148 can be configured as filling inserted in the space between adjacent light emitting units. The insulation layer 148 can be configured as filling inserted in the space between light emitting unit and the stopper. In some embodiments, the top surface 148a of the insulation layer 148 is planarized in order to provide a substantially flat surface for the second optical sensor 152 disposed thereon. In some cases, the top surface 148a is configured to be in touch with layer 16 or layer 18.

The second optical sensor 152 is designed to detect the intensity of ambient light entering into the device 10. The current into light emitting unit can adjusted according to the intensity detected by the second optical sensor 152. The second optical sensor 152 can be right above the light emitting unit or can be shifted. In some embodiments, there is only one second optical sensor 152 in the device 10. In some embodiments, there is only one second optical sensor 152 in the device 10. In some embodiments, there are several second optical sensors 152 and each second optical sensor 152 is designated to one light emitting unit.

In some embodiments, the optical sensor can be designed as shown in FIG. 8A. The optical sensor 153 is a two-sided sensor having one sensor 153a on surface and one sensor 153b on surface. The sensor 153a facing the window layer 18 is configured to detect the entered ambient light. The sensor 153a facing the electrode 145-1 and light emitting subpixel 145-2 is configured to detect the light emitted from the light emitting subpixel 145-2. The two sided optical sensor may be a composite structure having an insulation layer such as oxide disposed between two sensing area.

FIG. 8B depicts another embodiment showing an insulation film 149 is disposed over insulation layer 148. The insulation layer 148 is planarized before film 149 disposed thereon. A sensor 153b is disposed in the insulation layer 148 and facing the light emitting unit 145 to detect the intensity of light emitting subpixel 145-2. A sensor 153a is disposed over film 149 to detect the intensity of ambient light. In some embodiments, film 149 is planarized before the sensor 153a disposed thereon.

The optical sensor can be made with optical sensing material such as Mn, Zn, Mg, S, etc. In some embodiments, the optical sensor includes a ZnS compound disposed on an insulation substrate. The insulation substrate can be silicon oxide, silicon oxide, etc.

Besides the above advantages, some other circuits such as driver or touch sensor can be inserted between the light emitting units by shrinking down the size of the electrode 415-1 and light emitting subpixel 145-2. Another example described below can further facilitate a person with skill in the art to appreciate how the design window is improved.

FIG. 9 is a cross sectional view depicting another embodiment of deceive 10. A structure 210 is disposed over the insulation layer 148. The structure 210 can be configured as a part of a touch sensor. In some embodiments, the structure 210 is a capacitor. In some embodiments, the structure 210 is a resistor. In some embodiments, the structure 210 is a conductive trace connected with a capacitor or a resistor at one end.

Structure 210 can be embedded in layer 16 or 18 when it is configured as a part of a touch sensor. In some embodiments, the structure 210 has a lower light transmittance to the light emitting subpixel 145-2 than the electrode 145-1. In such case, the structure 210 is preferred to be misaligned with the light emitting subpixel 145-2 or the electrode 145-1 from a top view perspective.

FIG. 10 illustrate a top view of one embodiment of several different types of structures disposed over light emitting units 145. There are at least three different tiers stacking along the thickness direction. The light emitting units 145 are in the bottom and structures 210a, 210b, and 210e are between the light emitting units 145 and structures 210c, 210d, and 210f Structure 210e is a conductive trace connecting structures 210a, 210b. Structure 210f is a conductive trace connecting structures 210c, 210d. Structures 210a, 210b can be a capacitor so a resistor. Structures 210c, 210d can be a capacitor so a resistor.

Each structure is surrounded by light emitting units 145 and not overlapped with the light emitting units 145. Therefore, light emitted from the light emitting unit 145 can efficiently reach the window 18 without being blocked by the structures. Therefore, shrinking the size of the light emitting unit is not only to provide more opportunities to dispose optical sensor to real monitor the performance of each light emitting unit 145, but also provide more space to dispose other functional structures while still meeting the requirement of high density.

The foregoing outlines features of several embodiments so that persons having ordinary skill in the art may better understand the aspects of the present disclosure. Persons having ordinary skill in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other devices or circuits for carrying out the same purposes or achieving the same advantages of the embodiments introduced therein. Persons having ordinary skill in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alternations herein without departing from the spirit and scope of the present disclosure.

Claims

1. A light emitting device, comprising:

a substrate; and

a light emitting unit over the substrate, wherein the light emitting unit includes: a light emitting subpixel; and an electrode stacking on the light emitting subpixel along a vertical direction, the electrode including a width measured in a horizontal direction perpendicular to the vertical direction and the width is not greater than about 8 um.

2. The light emitting device in claim 1, wherein the electrode is a cathode of the light emitting unit.

3. The light emitting device in claim 1, further comprising an optical sensor adjacent to the light emitting unit and configured to detect emission intensity of the light emitting unit.

4. The light emitting device in claim 3, further comprising an array of thin film transistors (TFT) under the light emitting unit and the optical sensor is electrically connected to the TFT.

5. The light emitting device in claim 1, further comprising a stopper adjacent to the light emitting unit, wherein, along the vertical direction, the stopper has a thickness being greater than a thickness of the light emitting unit.

6. The light emitting device in claim 5, further comprising a through via in the stopper.

7. A light emitting device, comprising:

a substrate; and

an array of light emitting units over the substrate, wherein each light emitting unit of the array includes: an electrode; and a light emitting layer between the electrode and the substrate, wherein a horizontal width of the electrode is substantially equal to a horizontal width of the light emitting layer.

8. The light emitting device in claim 7, further comprising an insulation material filling a space between adjacent light emitting units.

9. The light emitting device in claim 7, further comprising a conductive trace to connect electrodes in a string.

10. The light emitting device in claim 7, further comprising an array of optical sensors, wherein each of the optical sensors is assigned to a corresponding light emitting unit.

11. The light emitting device in claim 7, further comprising an array of stoppers, wherein each stopper is between two adjacent light emitting units.

12. The light emitting device in claim 10, further comprising a conductive trace electrically connecting each optical sensor to a circuit in the substrate.

13. The light emitting device in claim 7, further comprising a touch sensor over the array of light emitting units, and an insulation layer between the touch sensor and the array of light emitting units.

14. The light emitting device in claim 13, wherein the touch sensor is surrounded by a plurality of light emitting units from a top view perspective.

15. The light emitting device in claim 14, wherein the touch sensor is laterally offset from the plurality of light emitting units from a top view perspective.

16. The light emitting device in claim 7, further comprising an array of optical sensors over the array of light emitting units, wherein the array of optical sensors are configured to detect ambient light emitted into the light emitting device.